Clutch drum assembly for automatic power transmission

ABSTRACT

A drum member has a circular base portion and a cylindrical side portion which is formed with holes at positions facing a brake band wrapping the drum member. A cylindrical member is coaxially disposed within the drum member with its one longitudinal end entirely secured to the inside surface of the circular base portion of the drum member. The cylindrical member is formed with holes or openings and is formed with longitudinally extending spline portions to which clutch plates are splined. The other end of the cylindrical member is entirely in contact with the inner surface of the cylindrical side portion of the drum member so that an enclosed chamber is defined by the drum member and the cylindrical member.

FIELD OF THE INVENTION

The present invention relates in general to an automatic powertransmission, more particularly to a clutch mechanism of thetransmission which functions to selectively connect and disconnect adriving and a driven element of the transmission. More specifically, thepresent invention is concerned with a high-and-reverse clutch of thetype having a clutch drum which is selectively tightened and released bya fluid operated brake band wrapping the same.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an automatic powertransmission having a clutch mechanism in which better lubricationbetween a clutch drum assembly and a brake band wrapping the assembly isachieved.

It is another object of the present invention to provide a low cost butefficient and light weight clutch drum assembly of a clutch for theautomatic power transmission.

SUMMARY OF THE DRAWINGS

Other objects and advantages of the present invention will become clearfrom the following description when taken in conjunction with theaccompanying drawings in which:

FIGS. 1(A) and 1(B) are sectional views of a transversely mounted typeautomatic power transmission in combination with a final drive unit, towhich an improved clutch mechanism according to the invention isapplied, the final drive unit being shown moved from its proper positionfor clearness of the drawing;

FIG. 2 is a fragmentary view, on an enlarged scale, of a portion of thetransmission seen in FIG. 1, showing the detail of the clutch mechanismof the present invention;

FIG. 3 is a fragmentary view taken in the direction of the arrow A shownin FIG. 2, several parts being not shown for clear showing of importantportions;

FIG. 4 is a fragmentary view, on an enlarged scale, of a clutchmechanism which is a modification of that shown in FIG. 2; and

FIGS. 5 and 6 are fragmentary views similar to that of FIG. 4, but showsconventionally used clutch mechanisms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to describing the detailed construction and configuration of theclutch mechanism of the invention, explanation of overall constructionof the transmission in which the clutch mechanism is employed will bemade with reference to FIGS. 1(A) and 1(B) in order to clarify theinvention.

Referring to FIG. 1 of the drawings, there is shown a transverselymounted type automatic power transmission 10 in combination with a finaldrive unit 168.

The transmission 10 comprises a converter housing 12 within which thetorque converter assembly 14 is housed. The torque converter assembly 14comprises a pump impeller 16, a turbine runner 18, and a stator 20 as iswell known in the art. The pump impeller 16 is connected via a convertercover 22 and a drive plate 24 to a crankshaft 26 of a power plant suchas an internal combustion engine (not shown) and is rotatable withcrankshaft 26 about an axis which is aligned with the axis of rotationof the crankshaft 26. Denoted by 28 is a pilot element which is securedto a central portion of the converter cover 22 and is received in acentral bore 30 of the crankshaft 26, as shown. The turbine runner 18 ismounted on a hub 32 which in turn is keyed or splined to a transmissionhollow input shaft 34 which has a center axis aligned with the axis ofrotation of the engine crankshaft 26. The stator 20 is positionedbetween the pump impeller 16 and the turbine runner 18 and is mounted ona stator support hollow shaft 36 through a torque converter one-wayclutch assembly 38. The stator support hollow shaft 36 has thetransmission hollow input shaft 34 axially passed therethrough insubstantially coaxial relationship and is fixedly but detachablyconnected through a flange portion 40 thereof to a base wall 12a of theconverter housing 12, as will be well understood hereinlater. The stator20 is permitted to rotate about the center axis of the input shaft 34 inthe same direction as the direction of the pump impeller 16 andaccordingly as the direction of rotation of the engine crankshaft 26. Anoil pump driving shaft 42 is rotatably and concentrically received inthe input shaft 34 and has a right end to which a hub 44 of theconverter cover 22 is splined or keyed. As will be understoodhereinlater, a left end of the oil pump driving shaft 42 is keyed with adrive gear 46a of a transmission oil pump assembly 46 which has an oilpump boby 46b bolted or otherwise secured to a stationary wall structureof a later-mentioned gear unit housing 48 of the transmission 10.

When the engine is in operation, the driving power produced by theengine is delivered from the engine crankshaft 26 to the pump impeller16 through the converter cover 22 and is transmitted from the pumpimpeller 16 to the input shaft 34 through the turbine runner 18 with atorque multiplied by means of the stator 20 at a ratio which is variablewith the ratio between the revolution speed of the engine crankshaft 26and that of the input shaft 34. The pump impeller 16 thus drives notonly the turbine runner 18 but also the transmission oil pump assembly46 through the oil pump driving shaft 42 so that the oil pump assembly46 delivers oil under pressure which is also variable with therevolution speed of the crankshaft 26 of the engine.

Within the gear unit casing 48 connected via bolts 49 to the converterhousing 12 is positioned a gear unit 50 of the transmission 10. The unit50 herein shown is arranged between the torque converter assembly 14 andthe oil pump assembly 46. The gear unit 50 comprises first and second orhigh-and-reverse and forward drive clutches 52 and 54 which arepositioned in a manner that the high-and-reverse clutch 52 is locatedbetween the oil pump assembly 46 and the forward drive clutch 54. Thehigh-and-reverse clutch 52 comprises a plurality of plates 56 keyed orsplined at their inner peripheral edges to a clutch hub 58 and plates 60keyed or splined at their outer peripheral edges to a first clutch drumassembly 62. Likewise, the forward drive clutch 54 comprises a pluralityof plates 64 keyed or splined at their inner peripheral edges to aclutch hub 66 and plates 68 keyed or splined at their outer peripheraledges to a second clutch drum 70. The clutch hub 58 for thehigh-and-reverse clutch 52 and the second clutch drum 70 for the forwarddrive clutch 54 are secured to each other and rotatable with the inputshaft 34 with the second clutch drum 70 keyed or splined at its innerperipheral portion to a left end portion of the input shaft 34. Theplate 56 of the high-and-reverse clutch 52 and the plates 68 of theforward drive clutch 54 thus serve as driving friction elements and,accordingly, the plates 60 of the high-and-reverse clutch 52 and theplates 64 of the forward drive clutch 54 serve as driven frictionelements in the clutches 52 and 54, respectively. Clutch pistons 76 and78 are respectively incorporated with the high-and-reverse clutch 52 andthe forward drive clutch 54 respectively for bringing the clutches 52and 54 into engagement when moved by a fluid fed into respective fluidchambers 80 and 82 which are formed between the clutch piston 76 and thefirst clutch drum assembly 62 and between the clutch piston 78 and thesecond clutch drum 70, respectively, as shown. Return springs 72 and 74are respectively incorporated with the high-and-reverse clutch 52 andthe forward drive clutch 54 to urge the pistons 76 and 78 in a directionto disengage the clutches 52 and 54, respectively.

The gear unit 50 further comprises first and second planetary gearassemblies 84 and 86 which are arranged at the right of the forwarddrive clutch 54 in the drawing. The first planetary gear assembly 84comprises an externally toothed sun gear 88 and an internally toothedring gear 90 which have a common axis of rotation aligned with thecenter axis of the input shaft 34. The ring gear 90 is formed on theclutch hub 66 for the forward drive clutch 54. The first planetary gearassembly 84 further comprises at least two planet pinions 92 each ofwhich is in mesh with the sun and ring gears 88 and 90 and is rotatableabout an axis around the common axis of rotation of the sun and ringgears 88 and 90. The planet pinions 92 of the first planetary gearassembly 84 are journaled on shafts of a pinion carrier 94. The secondplanetary gear assembly 86 is constructed similarly to the firstplanetary gear assembly 84 and thus comprises an externally toothed sungear 96 and an internally toothed ring gear 98 which have a common axisof rotation aligned with the center axis of the transmission hollowinput shaft 34. The sun gear 96 is integral with the sun gear 88 of thefirst planetary gear assembly 84. The united sun gears 88 and 96 of thefirst and second planetary gear assemblies 84 and 86, respectively, arejointly splined to a connecting shell 100 which encloses the forwarddrive clutch 54 and the first planetary gear assembly 84 and is securelyconnected to the first clutch drum assembly 62 for the high-and-reverseclutch 52. The second planetary gear assembly 86 further comprises atleast two planet pinions 102 each of which is in mesh with the sun andring gears 96 and 98 and is rotatable about an axis around the commonaxis of rotation of the sun and ring gears 96 and 98. The planet pinions102 of the second planetary gear assembly 86 are rotatably supported bya pinion carrier 104 having a drum portion 106 which leftwardly extendsto enclose in part the connecting shell 100 therein, as shown. By thereason which will become clear from the latter, the drum portion 106 ofthe pinion carrier 104 has a circular stop portion 108. The respectivesun gears 88 and 96 of the first and second planetary gear assemblies 84and 86 are formed with center bores through which a transmission hollowoutput shaft 110 having a center axis aligned with the center axis ofthe input shaft 34 is passed and axially extends toward the torqueconverter assembly 14. The output shaft 110 thus coaxially receivestherein the input shaft 34, as shown. The output shaft 110 has a leftend to which the pinion carrier 94 for the first planetary gear assembly84 is splined at its inner peripheral edge and has an intermediateportion to which the ring gear 98 for the second planetary gear assembly86 is connected through a generally disc shaped connecting member 112which is keyed or splined at its inner peripheral edge to theintermediate portion of the output shaft 110 and at its outer peripheraledge to the ring gear 98. Concentrically mounted around the drum portion106 of the pinion carrier 104 for the second planetary gear assembly 86is a low-and-reverse brake 114. This brake 114 comprises a plurality ofplates 116 keyed or splined at their inner peripheral edges to the drumportion 106 of the second planetary gear assembly 86, and a plurality ofplates 118 which are keyed or splined at their outer peripheral edges toan intermediate portion of the inner wall of the gear unit housing 48.The low-and-reverse brake 114 further has a drum shaped piston 120 whichis concentrically mounted around the first clutch drum assembly 62 forthe high-and-reverse clutch 52 and engages at its right end to theleftmost member of the plates 116 and 118. The left end portion of thepiston 120 is sealingly disposed in a fluid chamber 122 into which afluid under pressure is fed to move the piston 120 rightwardly urgingthe plates 116 and 118 of the brake unit 114 to be engaged with oneanother against a biasing force developed by return springs 124 whichare interposed between the left end portion of the piston 120 and aspring retainer 126 fixed to the oil pump body 46b via bolts 128. Asshown, the fluid chamber 122 is formed in the oil pump body 46b. Thelow-and-reverse brake 114 is paralleled in effect by a transmissionone-way clutch 130 which is positioned about the before-mentioned drumportion 106 for the second planetary gear assembly 86 and comprises astationary outer race member 132, a rotatable inner race member 134 anda series of spring loaded rollers 136 disposed between the outer andinner race members 132 and 134. The stationary outer race member 132 issplined to the inner wall of the gear unit housing 48. On the otherhand, the rotatable inner race member 134 is securely disposed on thebefore-mentioned circular step portion 108 of the drum portion 106 forthe second planetary gear assembly 86. The rollers 136 are arranged in amanner to be caused to stick to the outer and inner race members 132 and134 and thereby lock up the rotatable inner race member 134 to thestationary outer race member 132 when the inner race member 134 is urgedto turn about the center axis of the output shaft 110 in a directionopposite to the direction of rotation of the engine crankshaft 26, viz.,to the direction of rotation of the output shaft 110 to produce aforward drive mode of an automotive vehicle. The gear unit 50 of thetransmission 10 further comprises a brake band 138 which wrappes thecylindrical outer surface of the first clutch drum assembly 62 for thehigh-and-reverse clutch 52. Although not shown, the brake band 138 isanchored at one end to the gear unit housing 48 and is at the other endconnected to or engaged by a fluid operated band servo unit (not shown).Although, not shown in the drawing, a transmission governor assemblyindirectly driven by the output shaft 110 is arranged in the gear unithousing 48 in the vicinity of the ring gear 98 of the second planetarygear assembly 86. The body 46b of the before-mentioned oil pump assembly46 has a rightwardly extending sleeve portion 140 in which a fluidpassage 142 for lubrication fluid for the clutch assemblies 52 and 54 isformed. Indicated by numeral 144 is a parking gear which is secured onthe ring gear 98 for the second planetary gear assembly 86, forming partof a parking lock assembly to lock the output shaft 110 by the aid of aparking pawl (not shown) meshing with the parking gear 144 duringparking of the vehicle. Indicated generally by numeral 146 is ahydraulic control valve unit by which the gear unit 50 is controlled.

The output shaft 110 is integrally formed at its right section with anoutput gear 148 which has an axis of rotation aligned with the centeraxis of the output shaft 110. As will be understood from the drawing,the output gear 148 is situated within a chamber 150 which is defined bynot only an extension 152 of the base wall 12a of the cover housing 12but also the flange portion 40 of the stator support hollow shaft 36.The flange portion 40 is detachably connected to the base wall 12a bymeans of bolts 154. As shown, the extension 152 protrudes into theinterior of the gear unit housing 48 and has as its leading end portiona bearing opening (no numeral) within which is situated a tapered rollerbearing 156b. The flange portion 40 of the stator support hollow shaft36 is formed at a portion exposed to the chamber 150 of the output gear148 with a blind bore or bearing opening (no numeral) within which issituated another tapered roller bearing 156a. Inner races of thesebearings 156a and 156b are mounted on the transmission output shaft 110in a manner to put the output gear 148 therebetween. Meshing with theoutput gear 148 is an idler gear 158 which is supported by a pair oftapered roller bearings 160a and 160b. Inner races of these bearings160a and 160b are coaxially mounted on a sleeve shaft 162 which isconnected to the flange portion 40 of the before-mentioned statorsupport hollow shaft 36 by means of a bolt 164 passing through thesleeve shaft 162 in a manner that the axis of the idler gear 158 isparallel with the axis of the output gear 148. The idler gear 158 ismeshed with an externally toothed ring gear 166 forming part of thefinal drive unit 168.

The final drive unit 168 is positioned on a lateral side of thetransmission 10 and comprises a housing 170 integral with the converterhousing 12 and housing therein a differential case 172, a differentialpinion shaft 174 passing through the case 172, differential pinions 176rotatably disposed about the pinion shaft 174, and differential sidegears 178 each meshing with both the differential pinions 176 as isknown in the art. The case 172 has both lateral end portions on whichdifferential side bearings 180a and 180b are mounted. The right handbearing 180a is securely received in the bore of the housing 170, whilethe lefthand bearing 180b is received in a drum-shaped retainer 182which is detachably held in an opening (no numeral) formed in alaterally projected portion 48a of the gear unit housing 48. Denoted bynumeral 184 is a bolt for connecting the retainer 182 to the portion 48aof the gear unit housing 48. Extending away from the differential sidegears 178 are respective axle shafts 186a and 186b. The case 172 isintegrally formed with a connecting shell portion 188 which extendsleftwardly in this drawing and spacedly encloses in part the drum-shapedretainer 182. The connecting shell portion 188 has at the leading endthereof a flange 190 to which the above-mentioned externally toothedring gear 166 is fixed by means of bolts 192.

With this, the power train between the internal combustion engine andthe driving road wheels connected to the axle shaft 186a and 186b ismade up.

The transmission 10 incorporating with the final drive unit 168 operatesas follows:

                  TABLE 1                                                         ______________________________________                                                Clutches                                                                      High-  For-   Low &   One   Brake band                                        and-   ward   reverse way    (138)                                              Reverse  drive  brake clutch                                                                              Ap-  Re-                                Range     (52)     (54)   (114) (130) plied                                                                              leased                             ______________________________________                                        "P"                       O                                                   "R"       O               O              O                                    "N"                                                                                 "D.sub.1 "       O          O                                           Drive "D.sub.2 "       O                O                                           "D.sub.3 "                                                                            O        O                (O)  O                                "2"            O                  O                                                 2            O                  O                                       "1"                                                                                 1            O      O                                                   ______________________________________                                    

The high-and-reverse and forward drive clutches 52 and 54,low-and-reverse brake 114, one-way clutch 130 and brake band 138 of thetransmission mechanism or the gear unit 50 having the constructionhereinbefore described are operated in accordance with shedulesindicated in Table 1.

In Table 1, the sign "O" indicates that for each of thehigh-and-reverse, forward-drive and one-way clutches 52, 54 and 130 theclutch in question is in a coupled condition and for the low-and-reversebrake 114 the brake is in a condition applied. As to the brake band 138,the sign "O" in the column under "Applied" indicates that the brake band138 is actuated to lock up the first clutch drum assembly 62 and thesign "O" in the column under "Released" indicates that the brake band138 is released from the first clutch drum assembly 62. The sign "O"enclosed in the parentheses means that there is a fluid pressuredeveloped in the brake-apply chamber in the servo unit (not shown) butthe brake band 138 is released from the first clutch drum assembly 62with a fluid pressure also developed in the brake-release chamber of theservo unit.

The parking, reverse drive and neutral gear ranges and the automaticforward drive and manual second and first forward drive ranges asindicated in the leftmost column of Table are selectively established intransmission mechanism by manipulating a manual selector lever (notshown) which has positioned "P", "R", "N", "D", "2" and "1" respectivelycorresponding to the above-mentioned gear ranges.

When now the selector lever is in the parking range "P" or the neutralrange "N", both of the high-and-reverse and forward drive clutches 52and 54 are held in the uncoupled condition thereof so that the drivingconnection between the input and output shafts 34 and 110 is interruptedand as a consequence the output shaft 110 is maintained at rest eventhough the engine is in operation delivering its power output from thecrankshaft 26. Under these conditions, either the parking range or theneutral range is established in the transmission mechanism dependingupon whether the selector lever is held in the parking range "P" or inthe neutral range "N". If the selector lever is in the parking range"P", the low-and-reverse brake 114 is held in the condition applied sothat the drum portion 106 and accordingly the pinion carrier 104 of thesecond planetary gear assembly 86 are locked to the gear unit housing48. During parking of the vehicle, the parking gear 144 mounted on thering gear 98 for the second planetary gear assembly 86 is captured bythe parking pawl (not shown) of the before-mentioned parking lockassembly so that the output shaft 110 is locked up to the gear unithousing 48.

When the manual selector lever is moved into the automatic forward driverange "D" with the engine operating, the forward drive clutch 54 iscaused to couple. The power output delivered from the crankshaft 26 ofthe engine to the input shaft 34 through the torque converter assembly14 is transmitted through the forward drive clutch 54 and the clutch hub66 to the ring gear 90 of the first planetary gear assembly 84. The ringgear 90 is driven to rotate in the forward direction about the centeraxis of the output shaft 110 and thereby causes the sun gear 88 torotate in the opposite direction about the center axis of the outputshaft 110 through the planet pinions 92 each of which is rotated in thesame direction as the ring gear 90 about its own axis of rotation. Thesun gear 96 of the second planetary gear assembly 86, which is integralwith the sun gear 88 of the first planetary gear assembly 84, is rotatedin the opposite or reverse direction about the center axis of the outputshaft 110 and causes the ring gear 98 of the second planetary gearassembly 86 to turn in the forward direction about the center axis ofthe output shaft 110. Under these conditions, the individual planetpinions 102 of the second planetary gear assembly 86 are caused torotate in the forward direction about the respective axes of rotationthereof and therefore attempt to turn in the reverse direction about thecenter axis of the output shaft 110. The revolution of the pinioncarrier 104 of the second planetary gear assembly 86 is, however,prohibited by the one-way clutch 130 connected to the pinion carrier104, more specifically to the step portion 108 of the drum portion 106with the result that the pinion carrier 104 is locked to the gear unithousing 48 and acts as reaction elements for the ring gear 98 whichdrives via the disc-shaped connecting member 112 the output shaft 110 torotate in the forward direction about the center axis thereof. Theoutput shaft 110 is connected to the pinion carrier 94 of the firstplanetary gear assembly 84 so that each of the planet pinions 92 isrotated about the center axis of the output shaft 110 in the samedirection as the direction of rotation of the ring gear 90 of the firstplanetary gear assembly 84 but at a revolution speed which is lower witha certain ratio than the revolution speed of the ring gear 90 on whichthe planet pinions 92 are rolling, thereby creating the first forwardspeed or "low" gear ratio (D₁) in the transmission mechanism.

If the vehicle is thereafter sped up and the vehicle speed reaches acertain level, the band servo unit for the brake band 138 is actuated bya fluid distributed into the brake-apply fluid chamber of the servo unitand causes the brake band 138 to be tightened on the first clutch drumassembly 62 which is connected via the connecting shell 100 to theintegral first and second sun gears 88 and 96 for the first and secondplanetary gear assemblies 84 and 86. The sun gear 88 of the firstplanetary gear assembly 84 now acts as a reaction element for the planetpinions 92 which are being driven to turn in the forward direction aboutthe center axis of the output shaft 110 by the ring gear 90 rotatingwith the input shaft 34 through the forward drive clutch 54 which iskept coupled. The driving torque carried over to the ring gear 90 of thefirst planetary gear assembly 84 through the forward drive clutch 54 istherefore transmitted to the output shaft 110 by means of the planetpinions 92 and the associated pinion carrier 94. Under these conditions,the individual planet pinions 92 of the first planetary gear assembly 84are caused to rotate in the forward direction about the respective axisof rotation thereof and thus roll on the ring gear 90 while rotating inthe forward direction about the center axis of the output shaft 110. Theoutput shaft 110 is thus rotated in the forward direction about thecenter axis thereof at a speed higher than that achieved under the firstforward speed or "low" gear ratio (D₁) but lower with a certain ratiothan the revolution speed of the ring gear 90 of the first planetarygear assembly 84, thereby producing the second forward speed orintermediate ratio (D₂) in the transmission mechanism. Under the secondforward speed thus established, the output shaft 110 drives the ringgear 98 of the second planetary gear assembly 86 to rotate in theforward direction about the center axis of the output shaft 110 andthereby causes the planet pinions 102 to turn about the center axis ofthe output shaft 110 in the same direction as the direction of rotationof the ring gear 98. Thus, the pinion carrier 104 of the secondplanetary gear assembly 86 and accordingly the drum portion 106 are alsorotated in the forward direction about the center axis of the outputshaft 110 and cause the inner race member 134 of the transmissionone-way clutch 103 to run idle within the outer race member 132 of theone-way clutch 130.

As the vehicle speed further increases, a fluid is distributed into thebrake-release fluid chamber of the band servo unit for the brake band138 and causes the brake band 138 to be released from the first clutchdrum assembly 62 and, substantially at the same time, thehigh-and-reverse clutch 52 is actuated to couple. The power outputdelivered from the crankshaft 26 of the engine to the input shaft 34 isnow transmitted on one hand to the integral first and second sun gears88 and 96 of the first and second planetary gear assemblies 84 and 86through the high-and-reverse clutch 52 and the first clutch drumassembly 62 released from the brake band 138 and on the other hand tothe ring gear 90 of the first planetary gear assembly 84 by way of theforward drive clutch 54 and the clutch hub 66. It therefore follows thatthe sun gear 88 and the ring gear 90 for the first planetary gearassembly 84 are locked up so that the sun and ring gears 88 and 90 andthe planet pinions 92 therebetween as well as the output shaft 110connected to the planet pinion 92 by the pinion carrier 94 are driven torotate as a single unit in the forward direction about the center axisof the output shaft 110. The output shaft 110 is thus rotated in theforward direction about the center axis thereof at a speed substantiallyequal to the revolution speed of the input shaft 34, thereby providingthe third forward speed or "high" gear ratio (D₃) in the transmissionmechanism. Under the third forward drive speed thus established, theinput shaft 34 driven by the turbine runner 18 of the torque converter14 is rotated at a speed substantially equal to the revolution speed ofthe engine crankshaft 26 driving the pump impeller 16 of the converter14 and, as a consequence, there occurs no torque multiplication by thetorque converter 14, which thus functions merely as a fluid coupling.

When the manual selector lever is moved into the reverse drive range"R". The high-and-reverse clutch 52 and the low-and-reverse brake 114are actuated in the transmission mechanism. With the high-and-reverseclutch 52 thus engaged, the power output delivered from the crankshaft26 of the engine to the input shaft 34 by way of the torque converter 14is transmitted through the high-and-reverse clutch 52, first clutch drumassembly 62 and connecting shell 100 to the integral sun gears 88 and 96of the first and second planetary gear assemblies 84 and 86,respectively, causing the sun gears 88 and 96 to rotate in the forwarddirection about the center axis of the output shaft 110. Thelow-and-reverse brake 114 is being actuated to lock the drum portion 106and thus the pinion carrier 104 for the second planetary gear assembly86 is held stationary with respect to the gear unit housing 48, with theresult that the planet pinions 102 of the second planetary gear assembly86 are driven by the sun gear 96 for rotation in the reverse directionabout the center axis of the output shaft 110. This causes the outputshaft 110 to rotate in the reverse direction about the center axisthereof at a speed which is lower with a certain ratio than therevolution speed of the sun gears 88 and 96 of the first and secondplanetary gear assemblies 84 and 86 and accordingly of the input shaft34, establishing the reverse drive range "R" in the transmissionmechanism.

When the selector lever is in the manual second forward drive range "2",the forward drive clutch 54 and the brake band 138 are actuated and, asa consequence the output shaft 110 is driven to rotate in the forwarddirection about the center axis thereof by means of the pinion carrier94 of the first planetary gear assembly 84 as in the second forwardspeed (D₂) produced with the selector lever held in the automaticforward drive range "D".

Under the condition in which the selector lever is held in the manualfirst forward drive range position "1", either the low-and-reverse brake114 or the brake band 138 as well as the forward drive clutch 54 isactuated to lock the pinion carrier 104 of the second planetary gearassembly 86 or the integral sun gears 88 and 96 of the first and secondplanetary gear assemblies 84 and 86 depending upon the vehicle speed. Ifthe forward drive clutch 54 and the brake band 138 are actuated in thisinstance, the output shaft 110 is driven to rotate in the forwarddirection by the pinion carrier 94 of the first planetary gear assembly84 as in the second forward speed (D₂) established with the selectorlever held in the automatic forward drive range "D". If, on the otherhand, the forward drive clutch 54 and the low-and-reverse brake 114 areactuated in the manual forward speed range, the output shaft 110 isdriven to rotate in the forward direction about the center axis thereofby the ring gear 98 of the second planetary gear assembly 86 having thepinion carrier 104 held stationary with respect to the gear unit housing48, as in the first forward speed (D₁) produced with the selector leverheld in the automatic forward drive range "D". While the pinion carrier104 is locked to the gear unit housing 48 by the action of thetransmission one-way clutch 130 under the first forward speed producedin the automatic forward drive range, the pinion carrier 104 is lockedto the gear unit housing 48 by means of the low-and-reverse brake 114under the first forward speed produced in the manual first forward driverange. During the first forward speed in the manual first forward driverange, therefore a driving torque can be transmitted backwardly from thering gear 98 to the sun gear 96 through the planet pinions 102 in thesecond planetary gear assembly 86 and, for this reason, the engine brakecan be obtained.

The following description is directed to the detail in construction ofthe high-and-reverse clutch 52 to which the present invention isdirectly applied.

Referring to FIGS. 2 and 3, especially FIG. 2, there is partially shown,but on an enlarged scale, the high-and-reverse clutch 52 and itsincorporating parts. The clutch 52 comprises an outer drum member 200 ofpressed sheet metal construction which is firmly mounted at its annularbase portion 200a on a sleeve 202. The sleeve 202 is sealingly androtatably disposed about the sleeve portion 140 of the oil pump body 46bso that the drum member 200 and the sleeve 202 are rotatable about thesleeve portion 140 as a single unit. The cylindrical outer wall portion200b of the drum member 200 is formed with holes 204 through which alubricant oil is forced to pass for lubrication between contact surfacesof the drum member 200 and the brake band 138 as will be apparenthereinafter. An inner drum member 206 having pressed sheet metalconstruction is concentrically disposed within the outer drum member 200with its annular base portion 206a fixed as by welding to the insidesurface of the annular base portion of the drum 200 by usingelectronbeam welding technique. (It should be noted that the drum member200 and the drum member 206 constitute the before-mentioned "firstclutch drum assembly 62". ) The cylindrical inner side portion 206b ofthe inner drum member 206 has a small diameter section (no numeral)which defines the fluid chamber 80 for the piston 76, and a largediameter section (no numeral) which is wholly corrugated to havelongitudinally extending grooves 208 therethroughout, as will be seenfrom FIG. 3. The clutch plates 60 hereinbefore-mentioned are splined tothese grooves 208 to be movable longitudinally with respect to the innerdrum member 206. Indicated by numeral 210 is a sealing member disposedbetween the piston 76 and the small diameter section of the inner drummember 206. The large diameter section of the inner drum member 206 isformed at its open end with a radially outwardly projected circular lip212 which is entirely in contact with the inner surface of thecylindrical wall portion 200b of the outer drum member 200 so that anenclosed chamber 214 is defined between the drum members 200, 206 asshown. If desired, the lip 212 may be welded to the inner surface of thedrum member 200 to provide complete oil-tight sealing therebetween. Thecorrugated cylindrical side portion 206b of the inner drum member 206 isformed with holes 216 at the positions facing the holes 204 of the drummember 200. Denoted by numeral 218 is a snap ring secured to the innerdrum member 206 for limiting the rightward movements of the clutchplates 56 and 60.

Referring to FIG. 4, a modification of the clutch drum assembly 62 isshown. In this modification, a plurality of longitudinally extendingopenings 220 are formed in the cylindrical side portion 206b of theinner drum member 206 as a substitute for the aforementioned grooves208. Preferably, these openings 220 may be provided by punching orcutting machine. The clutch plates 60 are splined to these openings 220.

With the above-mentioned constructions of the high-and-reverse clutch52, the following advantageous phenomenon will arise upon rotation ofthe clutch drum assembly 62.

The rotation of the clutch drum assembly 62 tends to force the lubricantoil in the space surrounding the clutch plates 56 and 60 to moveradially outwardly by the centrifugal force thus exerted, so that thelubricant oil is forced to enter into the chamber 214 through the holes216 (or the openings 220 in case of FIG. 4) with the result that the oilthus entered into the chamber 214 is pressed against the inner surfaceof the cylindrical wall portion 200b of the drum member 200 to make apool 222 of the lubricant oil in a manner as is shown in FIG. 4. Itshould be noted that under rotation of the clutch drum assembly 62, thelubricant oil gathered in the chamber 214 has no exit except theopenings 204. Thus, a sufficient amount of lubricant oil is fed throughthe holes 204 into a clearance defined by the contact surfaces of thebrake band 138 and drum member 200 by the aid of the centrifugal forceexerted therein upon rotation of the clutch drum assembly 62, so thatoptimum lubrication is achieved between the brake band 138 and theclutch drum assembly 62.

In order to make the advantages of the invention clear, twoconventionally used clutch drum assemblies will be outlined withreference to FIGS. 5 and 6.

FIG. 5 shows a clutch drum 300 which is constructed of cast iron whichis machined to have a plurality of longitudinally extending splines 302.However, light weight and low cost construction and good productivityare not expected from this type clutch drum as is known in the art.

The clutch drum assembly 304 of FIG. 6 has a similar construction tothat of the invention and thus can solve the problems encountered in thecast iron type clutch drum 300 of FIG. 5. In the type of FIG. 6,however, effective oil distribution to the contact surfaces of the brakeband 138 and the drum member 200' via the holes 204 is not expected evenunder rotation of the clutch drum assembly 304 because almost all thelubricant oil in the chamber 214 escapes through a clearance 306 definedbetween the rightward end of the inner drum member 206' and the outerdrum member 200' in the direction of arrow 308.

What is claimed is:
 1. A power transmission having input and outputshafts, a clutch drum assembly, a brake band wrapping the clutch drumassembly to brake the same when actuated, first clutch plates splined attheir outer peripheral edges to the clutch drum assembly, and secondclutch plates splined to a hub member rotatable with the input shaft,with the first and second clutch plates being alternately arranged, saidclutch drum assembly comprising:an outer drum member having an annularbase portion and a cylindrical outer wall portion, said outer wallportion having an exterior surface contacted by said brake band, saidouter drum member being coaxial with and rotatable about the axis ofsaid input shaft; an inner drum member having a cylindrical inner wallportion with an annular base portion at one end thereof which is fixedto and in sealing contact with the annular base portion of said outerdrum member, said cylindrical inner wall portion being radially spacedfrom and being concentrically arranged within said cylindrical outerwall portion, said cylindrical inner wall portion being formed with aplurality of axially extending spline portions to which said firstclutch plates are splined, the opposite end of said cylindrical innerwall portion being shaped to provide a radially outwardly extendingintegral lip in sealing contact with said cylindrical outer wallportion, the radial spacing between said cylindrical inner and outerwall portions in combination with the sealing contact between saidannular base portions as well as between said lip and said cylindricalouter wall portion cooperating to define a fluid retaining chamberbetween said inner and outer drum members; and means for providing afluid communication between the interior of said inner drum member andsaid fluid retaining chamber, and between said fluid retaining chamberand the exterior surface of said outer wall portion.
 2. A powertransmission as claimed in claim 1 wherein said means comprise radiallyaligned openings in said inner and outer cylindrical wall portions.
 3. Apower transmission was claimed in claim 2 wherein the openings in saidinner cylindrical wall portion extend longitudinally and provide saidspline portions for said first clutch plates.
 4. A power transmission asclaimed in claim 1 wherein said inner and outer drum members areintegrally formed as sheet metal stampings.
 5. In a power transmission,a clutch drum assembly comprising:an outer drum member having an annularbase portion and a cylindrical outer wall portion, said outer wallportion having an exterior surface; an inner drum member formed, bypressing, from a sheet of metal, said inner drum member having acylindrical inner wall portion which is fixed at one end thereof insealing contact the annular base portion of said outer drum member, saidcylindrical inner wall portion being radially spaced from and beingconcentrically arranged within said outer wall portion, said cylindricalinner wall portion being formed with a plurality of axially extendingspline portions, the opposite end of said cylindrical inner wall portionbeing shaped to extend radially outwardly into sealing contact with saidcylindrical outer wall portion, the radial spacing between saidcylindrical inner and outer wall portions in combination with thesealing contact between the opposite ends of said inner drum and theannular base portion and cylindrical outer wall portion of said outerdrum cooperating to define a fluid retaining chamber between said innerand outer drum members; and means for providing a fluid communicationbetween the interior of said inner drum member and said fluid retainingchamber, and between said fluid retaining chamber and the exteriorsurface of said outer wall portion.